CODEWITHSUNDEEP
javaarraysmatrix
michael
michael

Reputation: 21

JAVA : How to create a snake shape matrix

Hi I am trying to create a matrix on the console using 2D array. The idea is that the output should look like this one :

1|8|9 |16
2|7|10|15
3|6|11|14
4|5|12|13

Is there any one who has an idea how it can be done?

Upvotes: 0

Views: 4617

Answers (4)

Joо
Joо

Reputation: 1

const matrix = [
  [1, 2, 3, 4],
  [5, 6, 7, 8],
  [9, 10, 11, 12],
  [13, 14, 15, 16],
];

let i = 1;

for (let col = 0; col < matrix[0].length; col++) {
  if (col % 2 === 1) {
    for (let row = matrix.length - 1; row >= 0; row--) {
      matrix[row][col] = i++;
    }
  } else {
    for (let row = 0; row < matrix.length; row++) {
      matrix[row][col] = i++;
    }
  }
}

console.table(matrix);

Upvotes: 0

michael
michael

Reputation: 21

finally with your help and after looking carefully at how multidimensional arrays work I solved the problem which now is looking quite simple to me.

int a = 4;
    int b = 4;
    int c = 1;
    boolean direction = true;
    int[][] arrey = new int[a][b];
    for (int y = 0; y <= b - 1; y++) {
        if (direction) {
            for (int x = 0; x <= a - 1; x++) {
                arrey[x][y] = c;
                c++;
            }
            direction = false;
        } else {
            for (int x = a - 1; x >= 0; x--) {
                arrey[x][y] = c;
                c++;
            }
            direction = true;
        }
    }

    for (int x = 0; x <= a - 1; x++) {
        for (int y = 0; y <= b - 1; y++) {
            System.out.print("["+arrey[x][y]+"]");
        }
        System.out.println("");
    }

Upvotes: 0

Rohit Jain
Rohit Jain

Reputation: 213281

Few things you can guess from the matrix: -

  • First, you have to traverse all rows of a columns first before moving to the next column

  • Second, you need to alternate between downwards and upwards direction on each iteration

  • So, you would need two nested for loop, for iterating through rows for a particular column. One will go from row 0 to max - 1, and the next will go from row = max - 1 to 0.

  • Now, to alternate the iteration direction, you can use a boolean variable, and toggle it after each iteration of inner loop finishes.

  • Each loop needs to be enclosed inside an if-else. Both of them will be executed on a certain condition. If boolean downwards = false;, then loop moving upwards will be executed and vice-versa.

  • On each iteration, fill the current cell with an integer counter, that you would have to initialize with 1, and increment it after each fill.

Pseudo code : -

    // Initialize variables row, col, and count = 1

    boolean goDown = true;

    int[][] matrix = new int[row][col];  // declare matrix

    for i = 0 to col:
        if (goDown)
            for j = 0 to row:  // Move in downwards direction
                assign count++ to matrix[j][i] 
                // assign to `[j][i]` because, we have to assign to rows first

            goDown = false;    // Toggle goDown

        else
            for j = row - 1 to 0:  // Move in upwards direction
                assign count++ to matrix[j][i] 

            goDown = true;  // toggle goDown

    }

Upvotes: 2

Erkan Haspulat
Erkan Haspulat

Reputation: 12562

Just some psuedo-code, hope it helps and gives you something to start with.

boolean goUp = false;
boolean goDown = true;
size = 4;
matrix[size][size];
k = 0; 
l =0;

loop i->0 i < size*size i++
  matrix[l][k] = i;

  if(l==size and goDown)
    goDown = false;
    goUp = true;
    k++;
  else if(l==0 and goUp)
    goDown = true;
    goUp = false;
    k++;
  else
    l = l+ (1*goDown?1:-1);
end loop;

Upvotes: 0

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